Composition for cleaning chemical mechanical planarization apparatus

ABSTRACT

The present invention relates to chemical compositions and methods of use for cleaning CMP equipment, including the interiors of delivery conduits carrying CMP slurry to the necessary sites. The chemical compositions of the present invention are also useful for post- CMP cleaning of the wafer itself. Three classes of cleaning compositions are described, all of which are aqueous solutions. One class operates in a preferable pH range from about 11 to about 12 and preferably contains one or more non-ionic surfactants, one or more simple amines, a surfactant or sticking agent such as one or more soluble dialcohol organic compounds and one or more quaternary amines. A second class of cleaning composition operates in a preferable pH range of approximately 8.5 and contains citric acid and oxalic acid. A third class of compositions is acidic, having a preferable pH range from about 1.5 to about 3, preferably containing at least one oxidizing acid, at least one chelating agent, at least one sticking agent and at least one anionic surfactant. HF and KOH are substantially absent from the preferred compositions of the present invention. Some compositions of the present invention are shown to be advantageously used for cleaning the slurry distribution system of CMP apparatus.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to the cleaning of equipment inwhich chemical mechanical planarization (“CMP”) is performed. Inparticular, the present invention relates to chemical compositions forcleaning CMP equipment wherein said compositions have improved cleaningperformance and/or reduced hazards to the equipment, human staff andenvironment.

[0003] 2. Description of Related Art

[0004] Planarization is a necessary step in the fabrication ofmultilayer integrated circuits (“ICs”), providing a flat, smooth surfacethat can be patterned and etched with the accuracy required of modem ICcomponents. The conventional planarization technique is CMP (ChemicalMechanical Planarization or Polishing) known in the art and described intext books (for example, “Chemical Mechanical Planarization ofMicroelectronic Materials,” by Joseph M. Steigerwald, Shyam P. Murarkaand Ronald J. Gutman, 1997). CMP typically makes use of a polishing padbrought into mechanical contact with the wafer to be planarized with anabrasive/reactive slurry interposed between polishing pad and wafer.Typical CMP slurries contain constituents that react chemically with thesubstrate to be planarized as well as constituents causing planarizationby mechanical abrasion. Relative motion of the polishing pad withrespect to the wafer leads to polishing of the wafer through mechanicalabrasion and chemical etching.

[0005] The abrasive slurry polishing materials used in CMP typicallycomprise an abrasive such as silica, alumina, or ceria and chemicallyreactive ingredients. Typically, in a practical production environment,these slurry materials cannot be entirely confined to the polishing padand often splash onto various portions of the CMP apparatus and dry inplace leading to increasing deposits of CMP slurry materials at variouslocations within and on the CMP apparatus itself. Deposits also tend toaccumulate on the interior surfaces of delivery tubes and other meansused for directing the CMP slurry to the necessary sites. As suchdeposits build over time, it is a common problem that portions of suchslurry deposits break loose in the typical form of abrasive paniclesthat can fall back onto the polishing pads, wafers and/or platens. Theseunwanted abrasive particles dislodged from slurry deposits on the CMPapparatus are a source of concern to the CMP engineer in that they maycause, inter alia, uncontrollable wafer scratching. Additionally, someslurry polishing materials such as ferric nitrate slurries typicallyused for CMP of tungsten layers cause unsightly stains on CMP apparatus.Hence, slurry materials and other substances have to be periodicallyremoved from CMP apparatus where they have been deposited. Whether theremoval occurs after each pad change, once a week, once a month, orpursuant to any other maintenance schedule does not negate the fact thatthe apparatus eventually has to be thoroughly cleaned so that slurry andother unwanted extraneous materials are removed therefrom.

[0006] Polishing slurries containing ferric nitrate Fe(NO₃)₃ tend toform ferric hydroxide (Fe(OH)₃) and ferric oxide (Fe₂O₃) residues thattend to precipitate within the conduits of slurry distribution systemsthat carry slurry to individual CMP apparatus and to specific locationswithin CMP equipment. These flocculent precipitates can break free,traverse through the slurry distribution system and come into contactwith the wafers. Undesirable wafer scratching may result. Hence, thereis a need for a cleaning composition effective for removing depositsfrom the interior regions of the slurry-carrying distribution systemsassociated with CMP apparatus.

[0007] Current practice makes use of surfactant solutions for cleaningCMP apparatus. These solutions are typically not chemically designed tobreak off or to dissolve typical CMP residues. Thus, the residues mustbe scraped off with, for example, Teflon scrappers. This scrapingtechnique is both laborious and time-consuming, and results in thegeneration of loose particles that may fall back onto the apparatus andeventually back onto polishing pads, wafers and/or platen.Uncontrollable wafer scratching and reduced product yields are thetypical results. Examples of CMP cleaning systems including wipingoperations include those commercially available from The Texwipe CompanyLLC of Upper Saddle River, N.J. for use in cleaning tungsten CMPslurries (TX8606 SCS) and oxide CMP slurries (TX8065 SCS).

[0008] Additionally, current methods for cleaning CMP apparatus make useof hydrogen fluoride (HF) solutions and/or potassium hydroxide (KOH)solutions. Typically, concentrated HF (49%), diluted HF (1% to 10%), ora dilute solution of KOH (e.g., a 5% to 10% solution) is employed. TheHF solution or KOH solution is typically sprayed onto the varioussurfaces of the CMP apparatus that require cleaning and subsequentlyrinsed with de-ionized (“DI”) water. The use of hydrogen fluoride (HF)for cleaning CMP apparatus has serious disadvantages as a result of thissubstance being extremely deleterious to the human bone structure ifabsorbed through the skin and as a result of it also being deleteriousif inhaled. HF also requires special disposal methods. Thus, stringentprecautions must be sustained when working with and disposing of HF.Additionally, HF fails to successfully remove some chemical stains suchas ferric nitrate. Furthermore, HF can also damage the platen plates ofCMP apparatus.

[0009] A multiplicity of disadvantages are also associated with the useof potassium hydroxide (KOH) for cleaning CMP apparatus. For one thing,KOH fails to successfully remove some chemical stains such as ferricnitrate. Additionally, KOH often leaves a residual composition ofpotassium, a mobile ion, on the apparatus and polishing pad that maycontaminate semiconductor wafers thereby resulting in detrimentaleffects on the electrical performance of the device and a reduction inyield. Furthermore, KOH can also damage the platen plates and some ofthe material used to form shields of the CMP apparatus (typicallyLexan). Although less dangerous to humans than HF, KOH is neverthelesscaustic and requires care in handling and disposal.

[0010] Thus, there is a need for a cleaning composition for removingunwanted deposits from CMP apparatus that ameliorates or overcomes oneor more of the shortcomings of the prior art. The cleaning compositionof the present invention is substantially free of HF, KOH. Furthermore,the present invention does not make use of HCl, in contrast to the workof Thurman-Gonzalez et. al. (WO 99/23688).

BRIEF SUMMARY OF THE INVENTION

[0011] The present invention relates to chemical compositions andmethods of use for cleaning CMP equipment, including the interiors ofdelivery conduits for carrying CMP slurry to the necessary sites. Thechemical compositions of the present invention are also useful forpost-CMP cleaning of the wafer itself.

[0012] Three classes of cleaning compositions are described, all ofwhich are aqueous solutions. One class operates in a preferable pH rangefrom about 11 to about 12 and preferably contains one or more non-ionicsurfactants, one or more simple amines, a surfactant or sticking agentsuch as one or more soluble dialcohol organic compounds and one or morequaternary amines. A second class of cleaning composition operates in apreferable pH range of approximately 8.5 and contains one or more oflactic acid, citric acid and oxalic acid. A third class of compositionsis acidic, having a preferable pH range from about 1.5 to about 3,preferably containing at least one oxidizing acid, at least onechelating agent, at least one sticking agent and at least one anionicsurfactant. HF and KOH are substantially absent from the preferredcompositions of the present invention.

[0013] Some compositions of the present invention are shown to beadvantageously used for cleaning the slurry distribution system of CMPapparatus.

[0014] Among the advantages of the present cleaning compositions are thefollowing:

[0015] One advantage of the cleaning compositions according to thepresent invention is that they clean better than cleaning compositionsbased upon both HF and KOH.

[0016] Another advantage of the cleaning compositions according to thepresent invention is that they are compatible with the typical plasticand metal parts of the CMP apparatus and thus are not as aggressive asHF and KOH in attacking the materials of the CMP apparatus.

[0017] A further advantage of the cleaning compositions according to thepresent invention is that they are far less caustic than HF.

[0018] Another advantage of the cleaning compositions according to thepresent invention is that they ameliorate environmental disposalrestrictions related to HF.

[0019] A further advantage of the cleaning compositions according to thepresent invention is that, lacking compounds capable of releasingpotassium ions, they do not leave a residual composition of potassiummaterial on the apparatus as occurs with the use of KOH.

[0020] Yet another advantage of the cleaning compositions according tothe present invention is that they tend to loosen residues therebyreducing the required manual labor. In some cases, the requirement ofusing a tool such as a spatula for scraping off residues from CMPapparatus is eliminated.

[0021] Another advantage of the cleaning compositions according to thepresent invention is that they typically require merely the use asponge, which does not have to be a SCOTCH bright sponge or the like,for removing residues. This tends to eliminate scratches to the CMPapparatus caused by cleaning with much harder and grittier, spongestypically used heretofore.

[0022] Yet another advantage of the present invention is the ability toclean residue from the interior surfaces of the CMP slurry distributionsystem.

[0023] Another advantage of the present invention is the absence ofabrasives.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] This application has no drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Several compositions are shown to be useful in the practice ofthe present invention as cleaning agents for CMP equipment. Thesecompositions can be used singly or in combination, and applied tovarious regions of the CMP apparatus requiring cleaning as specifiedherein or determined by routine experimentation on specific deposits.

COMPOSITION A

[0026] One composition pursuant to the present invention (“CompositionA”) comprises a solution of one or more non-ionic surfactants, one ormore simple amines, one or more soluble dialcohol organic compounds (orother substance compatible with the composition and functioning as asurfactant or sticking agent) and one or more quaternary amines, in anaqueous solution, typically de-ionized (“DI”) water.

[0027] The non-ionic surfactant should be soluble in the composition andcompatible with the pH ranges of the composition. Additionally, it isimportant that the cloud point of the surfactant be such as not torender the surfactant unstable when used in the cleaning composition.One non-ionic surfactant found useful in the present invention is3,5-dimethyl 1-hexyn-3-ol, the structure of which is given by thefollowing:

3,5-dimethyl 1-hexyn-3-ol

[0028] One useful commercial form of the above non-ionic surfactant issold by Air Products and Chemicals, Inc. under the tradenameSurf{overscore (y)}nol® 61. Other surfactants sold under Surf{overscore(y)}nol® tradenames include mono- and di-hydroxy compounds such as3,6-dimethyl-4-octyne-3,6-diol (Surf{overscore (y)}nol® 82),3,6-dimethyl-4-octyne-3,6-diol on an amorphous silica carrier(Surf{overscore (y)}nol® 82S) and tetramethyl decynediol (Surf{overscore(y)}nol® 104).

[0029] Monoethanolamine (MEA), or related primary amines, are useful inthe practice of the present invention so long as the particular aminecompound is sufficiently soluble in the cleaning composition. Otherfunctional groups may be present at the amine end of the molecule.Examples of such additional functional groups include hydroxyl, acid orester functionality and other amine groups (diamine, etc.) so long asthe primary amine nature of the molecule is preserved. Amines havingfrom 1 to about 8 carbons are useful in the practice of the presentinvention although the volatility of typical C₁ amines is a possibledisadvantage. The preferable range is C₂-C₆, tending to offer a goodbalance of non-volatility and solubility in the composition. Hydroxylfunctionality on the molecule is advantageous.

[0030] Propylene glycol may be used as a surfactant or sticking agent inthe practice of the present invention. Other such agents includedialcohol organic compounds such as ethylene glycol and the like so longas adequate solubility in the composition is present. Polymeric speciessuch as polyethylene oxide or polypropylene oxide may be used so long asthese polymeric species are adequately soluble in the composition andprecipitation problems in the composition are absent (which is thetypical situation occurring with reasonably low molecular weightspecies).

[0031] Tetramethylammonium hydroxide (TMAH) is typically used to adjustthe pH of the composition. The present cleaning composition may have apH in the range from about 10 to about 12.5 although the range fromabout 11 to about 12 is preferred. Variations of the present compositioncontaining greater or lesser amounts of MEA may also be used. A typicalmixture for Composition A follows: Typical Composition A ProportionsSolution Grams DI water 4700 Surfynol ® 61 60 Monoethanolamine (MEA) 300(@ 100% solution) Propylene Glycol 900 Tetramethylammonium Hydroxide(TMAH) 4

[0032] Composition A is particularly useful for silica based slurrysystems wherein the CMP apparatus is exposed to silica, water andperhaps hydrogen peroxide type of residues.

[0033] Moreover, and surprisingly, it was found that the Composition Aworked on a wide variety of residues including iron nitrate, alumina andsilica residues and worked irrespective of whether copper polishing,tungsten polishing or silica polishing had-been performed.

[0034] Furthermore, Composition A also may be used to some degree andunder certain conditions for cleaning semiconductor wafers. For example,Composition A can be used to clean semiconductor wafers after they arepolished. Normally, a wafer coming off a polishing apparatus is stillwet and the particles disposed thereon are not dry so that Composition Acan be used to remove them. Hence, Composition A can be used in both awet and a dry environment.

[0035] Preparation

[0036] Normally, the Composition A is prepared by first preparing acontainer of DI water to which the non-ionic surfactant (typically,Surf{overscore (y)}nol® 61) is added. Then, MEA is added followed by theaddition of propylene glycol. These are all liquids that they alldissolve and mix quite well simply with stirring. The pH is thenmeasured with a pH probe and TMAH is incrementally added to obtain afinal pH which is a preferably above about 11 but below about 12. Theseliquids are preferably continuously stirred within the container duringat least the time period during which the composition is prepared.

[0037] The container is typically an open-top container such as a beakeror bucket and is typically made of a plastic type of material suchpolypropylene, polyethylene, or the like. Stainless steel containers,black iron and glass containers should be avoided. Glass containers areknown in some cases to leach sodium into the solution contained therein,disadvantageous in the practice of the present invention.

COMPOSITION B

[0038] Another composition that was found to remove particles and metalion contamination is comprised of DI water, oxalic acid, citric acid,lactic acid, and one or more quaternary amines, choline hydroxide,tetramethylammonium hydroxide (TMAH), etc. This composition can be usedto remove particles, metal oxide and other metal salt contamination fromCMP apparatus and also can be employed to remove these same contaminantsfrom wafers polished with CMP slurries. The polished wafers can includecopper and tungsten.

[0039] Additionally, it has been found that this Composition B isespecially effective at removing iron, copper, zinc, potassium andcalcium contaminates. Typical Composition B Proportions (I) SolutionGrams DI water 658 Citric Acid  28 Lactic Acid  15.4 (@ 91% solution)Tetramethylammonium Hydroxide 206.2 (@ 25% solution in water) (TMAH)

[0040] Typically, tetramethylammonium hydroxide is used to adjust the pHof Composition B(I) to a desired final value. Composition B(I) has a pHof preferably about 8.5. Typical Composition B Proportions (II) SolutionGrams DI water 2,657.90 Citric Acid 115.15 Lactic Acid 63.35 Choline(two step addition, 618 gms + 45.6 663.60 gms)

[0041] Typically, choline is used to adjust the pH of Composition B (II)to a desired final value. Composition B(II) has a pH of preferably about9.0 and is stable during storage.

[0042] Preparation

[0043] Composition B(II) is typically prepared as described herein.,with modifications apparent to those having ordinary skills in the art.Preparation of Composition B(I) is analogous.

[0044] Typically, the required amount of DI water is added to acontainer, noting the weight and pH of the DI water. The first additionof choline is then typically performed, preferably with simultaneousstirring for a period of time, typically approximately 10 minutes. ThepH and temperature of the solution is typically noted and recorded. Itis expected that the pH is greater than about 13 following this firstaddition of choline, and that the temperature of the solution will beslightly lower than prior to addition of the choline. Next, lactic acidis typically added (for example, about 1.8% by weight), withsimultaneous stirring over a period of approximately 10 minutes. It isexpected that the pH will still exceed about 13 and the temperature willincrease somewhat. While stirring, citric acid is added to the solution,typically about 3.29% by weight. After about 10 minutes of stirring, atemperature rise is expected and the pH will typically drop toapproximately 6.5. The second addition of choline is performed insufficient mount to obtain the desired pH. typically a pH of 9.0 isdesired although a pH of 8.5 may also be used in the production of thepresent compositions. Small amounts of citric acid can be added to thesolution to increase the pH if the added choline reduces the pH toomuch, lying on the alkaline side of the desired pH.

COMPOSITION C

[0045] Another composition (Composition C), which is typically somewhatacidic, comprises DI water, hydroxylamine nitrate (HAN), a mildoxidizing acid in comparison with nitric acid, oxalic acid (as an agentfor chelating the iron residues that may be found on CMP apparatus), andan anionic surfactant, typically DOWFAX 8292 surfactant, and propyleneglycol which acts as a sticking agent so that the cleaning compositionwill stay in place for an effective period of time before draining offthe apparatus. Additionally, and in general, DOWFAX 8292 surfactant is asulfonic acid of a phenolic system. Furthermore, The Composition C wasdesigned particularly to remove iron residues from the CMP apparatus andthus, the use of the HAN and oxalic acid as components thereof.

[0046] Furthermore, Composition C also has utility in cleaningsemiconductor wafers to some degree and under certain conditions. Forexample, Composition C can be used to clean semiconductor wafers afterthey are polished. Normally, a wafer coming off a polishing apparatus isstill wet and the particles disposed thereon are not dry so thatComposition C can be used to remove them. Hence, Composition C can beused in both a wet and a dry environment. Typical Composition CProportions Solution Grams DI water 3,436.11 Hydroxylamine Nitrate (HAN)178 (@ 82% solution) Oxalic Acid 130 DOWFAX 8292 surfactant 0.89Propylene Glycol 660

[0047] Composition C has a general pH range from about 1 to about 4 anda preferred range from about 1.5 to about 3.

[0048] Preparation

[0049] Normally, Composition C is prepared by first adding DI water intoa container. HAN is then added to the DI water. Next, oxalic acid isadded which is then followed by the addition of the DOWFAX 8292surfactant. Finally, propylene glycol is added. These liquids arepreferably continuously stirred within the container during at least thecomposition preparation.

[0050] The container is typically an open-top container such a beaker orbucket and is typically made of a plastic type of material suchpolypropylene, polyethylene, or the like. Stainless steel containers,black iron and glass containers should be avoided. Glass containers areknown to leach sodium into the composition.

[0051] HAN is a fairly stable material and thus, substitution of a lessstable material such hydrogen peroxide would be disadvantageous. Nitricacid may be used but is not expected to be as efficient as HAN.Hydrochloric acid may be used but it has the disadvantage of possiblybeing corrosive to portions of the CMP apparatus. Sulfuric or phosphoricacid could also perhaps be used. However, these acids are not as good asan oxidizer in dilute solutions as HAN. Moreover, the mild oxidizingacid (HAN) is preferred according to the present invention.

[0052] Oxalic acid is a chelating agent and as such, any chelatingmaterial that is effectively binds iron (or other by products of the CMPprocess such as copper, tungsten, and iridium or other metal that mightbe polished) could be employed into this formulation in place of (or inaddition to) oxalic acid. For example, citric acid may replace orsupplement oxalic acid as chelating agent.

[0053] DOWFAX is an anionic surfactant and any surfactant that hasadequate solubility in this formulation and at this pH should beacceptable for use with this invention.

[0054] Ethylene glycol or some other dialcohol organic compound may beused in addition to (or in place of) propylene glycol as long as thecompounds are adequately soluble in the present cleaning solution.Additionally, polymer forms may be used. For example, polyethylene oxideor polypropylene oxide maybe used as long as the molecular weight is lowenough that there will be no precipitation problems occurring in theformulation. by the introduction and use of such polymers.

TYPICAL USE OF CLEANING COMPOSITIONS

[0055] When a user has completed the actual wafer polishing work for anumber of semiconductor wafers (CMP), or perhaps when the user isgetting ready to change out or replace the polishing pad, the cleaningcompositions according to the present invention are preferably sprayedonto the various surfaces of the CMP apparatus which are desired to becleaned. The surfaces thus sprayed are then allowed to stand for aperiod of time (e.g. from about 10 to about 30 minutes) to loosen up theresidues disposed thereon. The various surfaces of the CMP apparatus arethen wiped down with, for example, a polyurethane (or PVA) pad or spongethat preferably includes disposed thereon an amount of the cleaningcomposition according to the present invention. The various surfaces arethen thoroughly rinsed down, typically with DI water.

[0056] Additionally, Composition C, which is acidic, can be used toclean and remove deposits from slurry distribution systems.Specifically, Composition C can be used to clean and remove deposits offerric nitrate Fe(NO₃)₃ from distribution systems that typically includeat least one slurry holding means and associated distribution conduitsrunning to individual CMP apparatus.

[0057] In use, Composition C is pumped through the distribution systemin an amount to at least provide minimum pump volumes. Composition C istypically pumped through the slurry distribution system for a period oftime, perhaps one or more hours, in which all the conduits or lines areessentially flushed out. Next, distilled water may be pumped through thedistribution system to flush out Composition C. However, is should benoted that the distilled water step may not be necessary as a result ofComposition C being acidic and having a pH and an oxidizer system thatis compatible with the ferric nitrate Fe(NO₃)₃ slurries. That is, theferric nitrate Fe(NO₃)₃ slurries will typically remain in an oxidizedform when in contact with post-cleaning residual amounts of CompositionC, even absent a DI rinse. Notwithstanding, it is considered preferablein the practice of the present invention to employ a final distilledwater flush of the distribution system.

[0058] Having described the invention in detail, those skilled in theart will appreciate that, given the present disclosure, modificationsmay be made to the invention without departing from the spirit of theinventive concept described herein. Therefore, it is not intended thatthe scope of the invention be limited to the specific and preferredembodiments illustrated and described

We claim:
 1. A composition for removing chemical mechanicalplanarization residue comprising an aqueous solution containing at leastone non-ionic surfactant, at least one simple amine, at least onesticking agent, at least one quaternary amine, wherein said solution hasa pH from about 10 to about 12.5.
 2. A composition as in claim 1 whereinHF and KOH are substantially absent.
 3. A composition as in claim 1wherein said at least one non-ionic surfactant is selected from thegroup consisting of monohydroxyl compounds, dihydroxyl compound andmixtures thereof.
 4. A composition as in claim 3 wherein said at leastone non-ionic surfactant is 3,5-dimethyl 1-hexyn-3-ol.
 5. A compositionas in claim 1 wherein said at least one simple amine has from 1 to about8 carbon atoms.
 6. A composition as in claim 5 wherein said at least onesimple amine has from 1 to 6 carbons atoms.
 7. A composition as in claim5 wherein said at least one simple amine has hydroxyl functionality. 8.A composition as in claim 7 wherein said at least one simple amine ismonoethanolamine.
 9. A composition as in claim 1 wherein said at leastone sticking agent is a dialcohol organic compound.
 10. A composition asin claim 1 wherein said at least one sticking agent is selected from thegroup consisting of ethylene glycol, propylene glycol, polyethyleneoxide, polypropylene oxide and mixtures thereof.
 11. A composition as inclaim 1 wherein said at least one quaternary amine istetramethylammonium hydroxide.
 12. A composition as in claim 1 whereinsaid pH is from about 11 to about
 12. 13. A composition for removingchemical mechanical planarization residue comprising an aqueous solutioncontaining citric acid, lactic acid and at least one quaternary amine,wherein said solution has a pH of about 8.5.
 14. A composition as inclaim 13 wherein HF and KOH are substantially absent.
 15. A compositionas in claim 13 wherein said at least one quaternary amine istetraethylammonium hydroxide.
 16. A composition as in claim 13 whereinsaid citric acid is present in said composition at approximately doublethe amount by weight of said lactic acid.
 17. A composition for removingchemical mechanical planarization residue comprising an aqueous solutioncontaining at least one oxidizing acid, at least one chelating agent, atleast one sticking agent, at least one anionic surfactant, wherein saidsolution has a pH from about 1 to about
 4. 18. A composition as in claim17 wherein HF and KOH are substantially absent
 19. A composition as inclaim 17 wherein said at least one oxidizing acid is selected from thegroup consisting of nitric acid, sulfuric acid, phosphoric acid,hydroxylamine nitrate and mixtures thereof.
 20. A composition as inclaim 17 wherein said at least one chelating agent comprises oxalicacid, citric acid or mixtures thereof.
 21. A composition as in claim 17wherein said at least one sticking agent is selected from the groupconsisting of ethylene glycol, propylene glycol, polyethylene oxide,polypropylene oxide and mixtures thereof.
 22. A method of cleaningresidue from a chemical mechanical planarization slurry distributionsystem comprising: a) flowing the composition of claim 17 through saidslurry distribution system in an amount at least equal to the minimumvolume required by the pumping system; and, b) maintaining said slurryflow for a time sufficient to remove reside from said slurrydistribution system.
 23. A method as in claim 22 further comprising,immediately following step (b) thereof: c) flushing said slurrydistribution system with de-ionized water.